Related articles

Documents obtained from inside their Syrian territory reveal the cash-strapped group has slashed monthly salaries to just $50 (£34).

The files show militants receive an additional $50 (£34) for each wife, $35 (£24) for each child, $50 for each sex slave, $35 for each child of a sex slave, $50 for each dependent parent, and $35 each for other dependents.

But ISIS has lost a significant proportion of its income after bombing campaigns, and the latest haul of internal ISIS documents shed light on the realities of life under the group's barbaric rule.

ISIS fighters

Fri, March 25, 2016

Iraq and Syrian jihadists, including the Paris and Brussels attacks suspects.

Included in the austerity drive is an order to reduce electricity consumption in fighters' homes and a prohibition on the removal or sale of health equipment and medicine outside the caliphate, suggesting ISIS is running short on vital medical supplies.

One directive from senior commanders signals an intention to "cut the service line of 24/7 electricity from all the houses of the mujahideen brothers in the wilaya and preserving it for the bases only".

Defence analysts estimate ISIS territory has been reduced by as much as a third in recent months.

GETTY

Airstrikes have destroyed much of their income revenue

GETTY

Defence analysts estimate ISIS territory has been reduced by as much as a third in recent months

While the group once controlled a population of some nine million Syrians and Iraqis, that has since fallen to around six million, in part thanks to daily bombing raids by the US-led coalition and Russian jets.

Airstrikes have also destroyed much of their income revenue - through the bombing of oilfields and the reduction in tax-paying population - as well as vast cash stores held in warehouses in the region.

Aymenn Jawad al-Tamimi, a researcher in Islamic terrorism, predicted: "Populations under Islamic State rule are accustomed to poor living standards, exacerbated by years of civil war, and will likely stomach further decreases in quality of life."

Writing in the CTC Journal, he added: "Some internal documents point to reductions in 'perks' in recent months.

"The clearest example was a salary cut of 50 percent announced for all fighters in a Raqqa province."